1. Field of the Invention
This invention relates in general to a heat exchanger structure and, more particularly to a synthetic gas cooling apparatus or waste heat boiler which is provided with thermal protection means to avoid inadvertent operational damage. The hot gas producing process utilizes a fuel comprised of finely ground coal, coke, or even a liquid fuel which is combusted in a controlled atmosphere. The resulting effluent thus includes not only synthesis gas, but also an amount of dust or fly ash.
2. Description of the Prior Art
There are numerous heat exchanger designs such as waste heat boiler structures employed in different environments and for different applications. The cooling of hot synthesis gas from a gasifier, and the finely divided solids such as powdered fly ash or slag, has heretofore utilized radiation boilers which raise steam in water wall tubes. With such a boiler or heat exchanger, the solidified slag and cooled synthetic gas, are removed at the bottom of a downflow radiation boiler. In commercial size plants, however, the radiation boiler dimensions could become a limiting factor where a single, entrained throughput flow of the hot synthesis gas is employed.
It is further noted that various structures for heat exchangers such as radiant waste heat boilers, are utilized for transferring heat from the flow of hot gas that is to be cooled. Many of these structures are not readily adapted to large scale flow of synthesis gas. Also, there are known waste heat boilers that are characterized by a relatively complex structure; one such is described in U.S. Pat. No. 4,377,132.
Such structures, because of the excessive heat conditions under which they operate, are susceptible to damage in the event of some minor equipment malfunction. Further, the process might take a step not accounted for as a result of the presence of the solid segment of the hot produced gas.
It is therefor an object of the invention to provide a synthesis gas cooler structure that is adapted for safely conducting a high temperature, particle laden gaseous stream. A further object is to provide a unit of the type contemplated which can function without damage under operating conditions including a high temperature environment, in which a large amount of solids is carried in the hot gaseous stream.
It is a further object to provide a heat exchanger that will require a relatively brief shut down period for effecting internal replacements of parts.